The subject matter herein relates generally to flow meters and, more particularly, to an improved flow meter for use in determining a plurality of characteristics of a flow comprising more than one phase of matter such as liquid and gas (a “multiphase flow”) within a pipe.
Flow meters provide critical measurements concerning the characteristics of a multiphase flow within a pipe. For example, in the oil industry, there are various situations in which there is a need to use a flow meter to determine a fraction of the gas phase (the “gas fraction”) and a fraction of the liquid phase (the “liquid fraction”) comprising the multiphase flow. A dual venturi flow meter can be used for this purpose. In a typical dual venturi flow meter, there are two constrictions, each being formed by a separate constricting conical section and a separate expanding conical section. Differences in pressure of the multiphase flow across the constrictions bear an empirical relationship to the gas fraction and the liquid fraction. The differences in pressure can be determined from data generated by pressure sensors mounted within the flow meter. Each pressure sensor has a face that can be susceptible to erosion as a result of impingement from particles, such as sand, present within the multiphase flow. This susceptibility is exacerbated if the face protrudes from an interior wall of the pipe.
Also in a typical venturi flow meter, the constricting conical sections constrict at an angle of thirty degrees, and the expanding conical sections expand at an angle of five degrees. The angle of the expanding conical sections in particular can significantly add to the length of the flow meter. The length of the flow meter can be ten to fifteen times the diameter of the pipe, and the diameter can be between 76.2 centimeters (thirty inches) and 114.3 centimeters (forty-five inches).
The aggregate lengths of a dual venturi flow meter and a second type of flow meter can be prohibitive of their collective serial installation within a subsea Christmas tree, which is an assembly of valves, spools, and fittings used to control the flow into or out of a subsea well, such as an oil well or a gas well. Examples of subsea Christmas trees include conventional, dual bore, mono bore, through flow line (TFL), horizontal, mudline horizontal, side valve, and through bore tree (TBT) trees. In a practical use case scenario, after the gas fraction and the liquid fraction are determined using a dual venturi flow meter, it may be desirious to determine a liquid composition of the multiphase flow using a water cut flow meter. The liquid composition can indicate the amount of liquid hydrocarbons and the amount of water present in the liquid fraction. However, the amount of space within a subsea Christmas tree may not accommodate both a dual venturi flow meter and a water cut flow meter for use in determining each of the gas fraction, the liquid fraction, and the liquid composition.
It would be advantageous to provide a flow meter that can be used within a subsea Christmas tree to determine a plurality of characteristics of a multiphase flow that are typically determined through use of a dual venturi flow meter and a second type of flow meter, and that shelters devices mounted therein from impingement by particles within the multiphase flow.